The present invention relates to a calibration method for use in a head loading/unloading type disk apparatus and, more particularly, to a calibration method suited to automatic adjustment of the velocity detection value used in unloading.
Recently, some disk apparatuses for recording and reproducing information by using a head, e.g., some small magnetic disk apparatuses use a head retraction method called a loading/unloading method. The characteristic feature of this loading/unloading method is as follows. When no data read/write operation is performed, e.g., when the rotation of a disk (recording media) is stopped, a head stops on a ramp mechanism positioned outside the outer periphery of the disk. In this state, the head is moved from a retraction position on the ramp mechanism onto the disk by an instruction from a host to thereby perform a read/write operation. When the read/write operation is complete, the head is returned from the disk onto the ramp mechanism.
The operation of moving the head from the ramp mechanism onto the disk is called loading, and the operation of moving the head from the disk onto the ramp mechanism is called unloading.
Jpn. Pat. Appln. KOKAI Publication No. 8-63920 has disclosed an apparatus for loading and unloading an arm having a head slider to and from a rotary information recording disk by driving the arm by an actuator. In this apparatus, the back electromotive force of a voice coil type driving mechanism of the actuator is detected and fed back to a driving control circuit, and this control circuit controls the position and velocity of the actuator. That is, this reference describes that when loading or unloading is performed, velocity feedback control is performed by detecting the VCM velocity by using the back electromotive force generated in the voice coil motor (VCM).
In this prior art, however, which performs velocity feedback control by detecting the VCM velocity by using the back electromotive force generated in the voice coil motor (VCM), if the resistance of the coil of the VCM changes due to temperature change or the like, the relationship between the value (VCM current value) of current flowing through the VCM and the VCM velocity detection value also changes. This makes accurate velocity feedback control impossible to perform. The above reference does not describe the nature of the problem and a method of solving the problem when the resistance of the coil of the VCM changes due to temperature change or the like and the relationship between the VCM current value and the VCM velocity detection value changes.
Accordingly, it is an object of the present invention to provide a calibration method capable of accurately correcting the relationship between the value of a voice coil motor current flowing through a voice coil motor and a voice coil motor detection value detected by a voice coil motor velocity detection circuit, thereby performing accurate feedback control during loading/unloading.
It is another object of the present invention to provide a calibration method capable of improving the accuracy of a detected velocity by detecting a state in which the VCM resistance changes due to temperature change or the like and this may change the relationship between the VCM current value and the VCM velocity detection value, thereby performing more accurate velocity feedback control.
According to one aspect of the present invention, there is provided a calibration method for use in a head loading/unloading type disk apparatus having a voice coil motor for driving a carriage to move a head in a direction of radius of a disk, a voice coil motor velocity detection circuit for detecting a voice coil motor velocity corresponding to a back electromotive force of the voice coil motor, and a ramp mechanism arranged outside an outer periphery of the disk to retract the head, comprising the steps of: executing, at the start of loading control for loading the head from the ramp mechanism onto the disk, calibration for correcting a relationship between a value of a voice coil motor current flowing through the voice coil motor and the voice coil motor velocity detection value detected by the voice coil motor velocity detection circuit, the calibration being executed by obtaining a voice coil motor velocity detection value detected by the voice coil motor velocity detection circuit in a state where an actual velocity of the voice coil motor is set to zero and a current is supplied to the voice coil motor; and periodically reexecuting the calibration after the head is loaded.
In the present invention, a relationship between a value of a voice coil motor current flowing through the voice coil motor and the voice coil motor velocity detection value detected by the voice coil motor velocity detection circuit is accurately corrected by the calibration. The calibration is executed by obtaining a voice coil motor velocity detection value detected by the voice coil motor velocity detection circuit in a state where an actual velocity of the voice coil motor is set to zero and a current is supplied to the voice coil motor. With this the calibration, the velocity detection value detected by the VCM velocity detection circuit can be accurately corrected by velocity feedback control during unloading. This makes accurate unloading possible.
Generally, when a predetermined time or more has elapsed from loading, the resistance of the VCM coil changes due to temperature change, and this causes an error in the aforementioned relationship corrected by the calibration. So, (velocity feedback control during) unloading may not be accurately performed. In the present invention, however, the calibration is periodically reexecuted after loading. Accordingly, unloading can be accurately performed regardless of the reception timing of an unload instruction.
According to another aspect of the present invention, there is provided a calibration method for use in a head loading/unloading type disk apparatus having a voice coil motor for driving a carriage to move a head in a direction of radius of a disk, a voice coil motor velocity detection circuit for detecting a voice coil motor velocity corresponding to a back electromotive force of the voice coil motor, and a ramp mechanism arranged outside an outer periphery of the disk to retract the head, comprising the steps of: executing, at the start of loading control for loading the head from the ramp mechanism onto the disk, calibration for correcting a relationship between a value of a voice coil motor current flowing through the voice coil motor and the voice coil motor velocity detection value detected by the voice coil motor velocity detection circuit, the calibration being executed by obtaining a voice coil motor velocity detection value detected by the voice coil motor velocity detection circuit in a state where an actual velocity of the voice coil motor is set to zero and a current is supplied to the voice coil motor; and if it is detected that a change in a temperature of the voice coil motor or an ambient temperature thereof from a temperature during loading is not less than a prescribed value after the head is loaded, reexecuting the calibration.
When the VCM coil resistance changes due to temperature change, the aforementioned relationship corrected during loading cannot reflect the present state any longer, and the error increases. This may make accurate unloading impossible. In the present invention, however, if the change in the VCM temperature from that during loading is equal to or larger than a prescribed value, the calibration is reexecuted. Consequently, accurate unloading can be performed.
According to still another aspect of the present invention, there is provided a calibration method for use in a head loading/unloading type disk apparatus having a voice coil motor for driving a carriage to move a head in a direction of radius of a disk, a voice coil motor velocity detection circuit for detecting a voice coil motor velocity corresponding to a back electromotive force of the voice coil motor, and a ramp mechanism arranged outside an outer periphery of the disk to retract the head, comprising the steps of: executing, at the start of loading control for loading the head from the ramp mechanism onto the disk, calibration for correcting a relationship between a value of a voice coil motor current flowing through the voice coil motor and the voice coil motor velocity detection value detected by the voice coil motor velocity detection circuit, the calibration being executed by obtaining a voice coil motor velocity detection value detected by the voice coil motor velocity detection circuit in a state where an actual velocity of the voice coil motor is set to zero and a current is supplied to the voice coil motor; reading out the voice coil motor velocity detection value immediately after loading control is switched to on-track control from the voice coil motor velocity detection circuit and storing the readout value in a memory; and monitoring the voice coil motor velocity detection value detected by the voice coil motor velocity detection circuit while the head is positioned on the disk and, if an absolute value of a difference between the monitored voice coil motor velocity detection value and the voice coil motor velocity detection value stored in the memory is not less than a prescribed value, reexecuting the calibration.
If the absolute value of the difference between the VCM velocity detection value detected immediately after loading control is switched to on-track control and the VCM velocity detection value monitored while the head is positioned on the disk (in the head positioning control state), i.e., the VCM velocity detection value difference is equal to or larger than a prescribed value, it is highly likely that the VCM coil resistance has changed. If this is the case, the error in the aforementioned relationship corrected during loading increases, so unloading may not be accurately performed. In the present invention, however, if the VCM velocity detection value difference is equal to or larger than a prescribed value, the calibration is reexecuted. Consequently, accurate unloading can be performed.
The calibration can also be reexecuted by moving the carriage to the inner-periphery stopper position. If this is the case, the carriage is pushed against the inner-periphery stopper to realize zero VCM velocity, so the calibration can be done with high accuracy.
It is also possible to reexecute the calibration by moving the carriage to the outer-periphery stopper position by unloading and to reload after the calibration. If this is the case, the carriage is pushed against the outer-periphery stopper to realize zero VCM velocity, so the calibration can be done with high accuracy.
According to still another aspect of the present invention, there is provided a calibration method for use in a head loading/unloading type disk apparatus having a voice coil motor for driving a carriage to move a head in a direction of radius of a disk, a voice coil motor velocity detection circuit for detecting a voice coil motor velocity corresponding to a back electromotive force of the voice coil motor, and a ramp mechanism arranged outside an outer periphery of the disk to retract the head, comprising the steps of: executing, at the start of loading control for loading the head from the ramp mechanism onto the disk, calibration for correcting a relationship between a value of a voice coil motor current flowing through the voice coil motor and the voice coil motor velocity detection value detected by the voice coil motor velocity detection circuit, the calibration being executed by obtaining a voice coil motor velocity detection value detected by the voice coil motor velocity detection circuit in a state where an actual velocity of the voice coil motor is set to zero and a current is supplied to the voice coil motor; and if a predetermined time has elapsed since the head is loaded when an unload instruction is received, reexecuting the calibration and performing unloading thereafter.
As already described above, when a predetermined time or more has elapsed from loading, the VCM coil resistance changes due to temperature change, and this increases an error in the aforementioned relationship corrected during loading. So, unloading may not be accurately performed. In the present invention, however, the elapsed time from loading is checked when an unload instruction is received. If a predetermined time or more has elapsed, the calibration is reexecuted, and then unloading is performed. Therefore, accurate unloading can be performed.
According to still another aspect of the present invention, there is provided a calibration method for use in a head loading/unloading type disk apparatus having a voice coil motor for driving a carriage to move a head in a direction of radius of a disk, a voice coil motor velocity detection circuit for detecting a voice coil motor velocity corresponding to a back electromotive force of the voice coil motor, and a ramp mechanism arranged outside an outer periphery of the disk to retract the head, comprising the steps of: executing, at the start of loading control for loading the head from the ramp mechanism onto the disk, calibration for correcting a relationship between a value of a voice coil motor current flowing through the voice coil motor and the voice coil motor velocity detection value detected by the voice coil motor velocity detection circuit, the calibration being executed by obtaining a voice coil motor velocity detection value detected by the voice coil motor velocity detection circuit in a state where an actual velocity of the voice coil motor is set to zero and a current is supplied to the voice coil motor; and if a change in a temperature of the voice coil motor or an ambient temperature thereof from the temperature during loading is not less than a prescribed value when an unload instruction is received, reexecuting the calibration and performing unloading thereafter.
As already described above, if the VCM coil resistance changes due to temperature change, the aforementioned relationship corrected during loading cannot reflect the present state any longer, and the error increases. This may make accurate unloading impossible to perform. In the present invention, however, if the change in the VCM temperature from that during loading is equal to or larger than a prescribed value, the calibration is reexecuted, and then unloading is performed. Therefore, accurate unloading can be performed.
According to still another aspect of the present invention, there is provided a calibration method for use in a head loading/unloading type disk apparatus having a voice coil motor for driving a carriage to move a head in a direction of radius of a disk, a voice coil motor velocity detection circuit for detecting a voice coil motor velocity corresponding to a back electromotive force of the voice coil motor, and a ramp mechanism arranged outside an outer periphery of the disk to retract the head, comprising the steps of: executing, at the start of loading control for loading the head from the ramp mechanism onto the disk, calibration for correcting a relationship between a value of a voice coil motor current flowing through the voice coil motor and the voice coil motor velocity detection value detected by the voice coil motor velocity detection circuit, the calibration being executed by obtaining a voice coil motor velocity detection value detected by the voice coil motor velocity detection circuit in a state where an actual velocity of the voice coil motor is set to zero and a current is supplied to the voice coil motor; reading out the voice coil motor velocity detection value immediately after loading control is switched to on-track control from the voice coil motor velocity detection circuit and storing the readout value in a memory; and monitoring the voice coil motor velocity detection value detected by the voice coil motor velocity detection circuit when an unload instruction is received and, if an absolute value of a difference between the monitored voice coil motor velocity detection value and the voice coil motor velocity detection value stored in the memory is not less than a prescribed value, reexecuting the calibration and performing unloading thereafter.
As already described above, if the difference between the VCM velocity detection values is equal to or larger than a prescribed value, it is highly likely that the VCM coil resistance has changed. So, the aforementioned relationship corrected during loading can no longer reflect the present state, and the error increases. This may make accurate unloading impossible. In the present invention, however, if the difference between the VCM velocity detection values is equal to or larger than a prescribed value, the calibration is reexecuted, and then unloading is performed. Therefore, accurate unloading can be performed.
The reexecution of the calibration when the unload instruction is received can also be performed by moving the carriage to the inner-periphery stopper position. If this is the case, the carriage is pushed against the inner-periphery stopper to realize zero VCM velocity, so the calibration can be done with high accuracy.
According to still another aspect of the present invention, there is provided a calibration method for use in a head loading/unloading type disk apparatus having a voice coil motor for driving a carriage to move a head in a direction of radius of a disk, a voice coil motor velocity detection circuit for detecting a voice coil motor velocity corresponding to a back electromotive force of the voice coil motor, and a ramp mechanism arranged outside an outer periphery of the disk to retract the head, comprising the steps of: executing, at the start of loading control for loading the head from the ramp mechanism onto the disk, calibration for correcting a relationship between a value of a voice coil motor current flowing through the voice coil motor and the voice coil motor velocity detection value detected by the voice coil motor velocity detection circuit, the calibration being executed by obtaining a voice coil motor velocity detection value detected by the voice coil motor velocity detection circuit in a state where an actual velocity of the voice coil motor is set to zero and a current is supplied to the voice coil motor; when an unload instruction is received, performing unloading by using a result of the calibration during loading; and if the unloading indicates abnormality, moving the carriage to an inner-periphery stopper position, reexecute the calibration, and again performing unloading by using a result of the reexecuted calibration.
When unloading control is performed in accordance with an unload instruction, unloading may not be accurately performed depending on the error in the aforementioned relationship corrected during loading. Unloading abnormality occurs if the VCM current value during unloading control does not reach a current value by which the head can be unloaded to the ramp mechanism. If this is the case, it is highly likely that the head is not present on the ramp mechanism. In the present invention, therefore, if unloading abnormality occurs, the carriage is moved to the inner-periphery stopper position and pushed against the inner-periphery stopper. In this state, the calibration is reexecuted, and unloading is again performed by using this updated velocity correction value. This makes accurate unloading feasible.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.